Hard metal alloy



Patented June 1, 1937 UNITED. STATES PATENT OFFICE HARD METAL ALLOY Alan Richard Powell and Ernest Robert Box, London, England, assignors to Johnson Matthey & Company, Limited 6 Claims.

This application is a division of our copending parent application Serial No. 692,219, filed October 4th, 1933, and is filedin response to a final requirement of division therein. Said application has matured into Patent No. 2,070,451, granted Feb. 9, 1937.

This invention relatesto the manufacture and production of hard metal alloys especially useful for tipping the points of gold nibs and the points of compass needles.- Such alloys in addition to great hardness must be resistant to tarnishing and to corrosion by dilute solutions of the common acids and alkali, must have a high resistance to wear, must be capable of being readily soldered onto gold and onto copper and iron base metal alloys and must be sufliciently tough not to chip or splinter when subjected. to grinding, polishing or slitting operations. At one time native grains of osmiridium were solely used for these purposes but the supplies of this natural product are not sufilciently uniform in size and shape; hence numerous alloys have been made for this purpose by melting together some or all of' the constituents of osmiridium with other metals of the platinum group with or without the addition of base metals to increase the hardness. Efiorts to convert native osmiridium into grains suitable of iridium and 0 to 20 per cent of ruthenium) or of osmium and/or ruthenium together with an element of the group consisting of cobalt and nickel (3 to 25 per cent) and boron (0.1 to 5 per cent). The alloy should contain at least per cent of osmiridium or of osmium and/or ruthenium. 4

In making the alloys the constituents may be mixed together in the form of powde rs'or small grains and the mixture melted in a suitable furnace as, for example, an electric furnace of the induction, resistance or are type; We prefer however to add the boron in the form of an alloy with the element of the group consisting of cobalt and nickel for example as cobalt boride.

The best alloys are those the proportions of the components of which are within the following ranges:-

Boron, the boron being added in the form of a cobalt boron alloy containing 10 per cent of boron 0.5

Earample 2 Per cent Native osmiridium 90 Cobalt 9 Boron, the boron being added in the form 'of cobalt boride--. 1

We claim: 1. A hard metal alloy of the kind defined consisting of '75 to 94.5% of at least one metal of the group consisting of osmiridium, osmium and I ruthenium, 3 to 25% of at least one metal of the group consisting of cobalt and nickel, and 0.1 to 5% boron.

2. A hard metal alloy of the kind defined consisting of '75 to 94.5% of at least one metal of the group consisting of osmiridium, osmium and ruthenium, 3 to 25% cobalt, and 0.1 to 5% boron.

3. A hard metal alloy of the kind defined consisting of 75 to 94.5% of at least one metal of the group consisting of osmiridium, osmium and ruthenium, 3 to 25% of a metal of the group consisting of cobalt and nickel, and 0.1 to 5% boron added as a boride of the said metal of the group consisting of cobalt and nickel.

4. A hard metal alloy of the kind defined consisting of, 75 to 94.5% of osmiridium, 3 to 25% of at least one metal of the group consisting of cobalt and nickel, and 0.1 to 5% boron.

5. A hard metal alloy of the kind defined consisting of to of osmiridium, 19.5% to 9% of cobalt, and 0.5 to 1% of boron.

6. A hard metal alloy of the kind defined con- ALAN RICHARD POWELL. ERNEST ROBERT BOX. 

